This invention relates to an apparatus and method for the testing of semiconductor devices, and in particular to the testing of such devices in a singulated form.
Semiconductor circuits are initially manufactured as wafers. A circular wafer of a semiconductor material such as silicon is formed with a plurality of individual circuits each of which is called a die (pl. dice). After the dice are formed on the wafer, the wafer is cut so as to separate the dice from each other and each die is then assembled into a semiconductor package with bond wires connecting the bond pads of a die with the pins of the package. A number of tests on the dice are carried out at various stages in the process. In particular, for example, a test of the devices while they are still part of the wafer is carried out. This test is known as a wafer test and is used to discard dies that have been incorrectly formed.
Once the die is assembled in a package it is tested again to ensure that the package has been properly assembled and that no damage has occurred to the die during the assembly and processing and to verify that the device still meets its design specifications. This test may be carried out at several different temperatures to check parameters that may be temperature sensitive. For example commercial devices may be tested at 0xc2x0 C., 25xc2x0 C. and 70xc2x0 C. Devices intended for military applications may be tested at more extreme temperatures still, for example xe2x88x9255xc2x0 C., 25xc2x0 C. and 125xc2x0 C.
It should also be understood that the processing of semiconductor devices is conventionally divided into two categories: front end processing and back end processing. Front end processing includes such processes as the manufacture of die bearing wafers and the separation of the dice from the wafer. Front end processing is usually highly automated. Back end processing, on the other hand, includes device assembly and packaging processes, and these processes are more widely diverse in their nature and the degrees of automation. To supply components to diverse back end processing apparatus and methods results in a number of different methods of delivering the semiconductor dice, with the main choice being between delivering the components in non-singulated form attached to a leadframe, or in a singulated form. Testing processes and apparatus, which may conventionally come between front and back end processing, may therefore need to be highly flexible and capable of testing a large number of devices with a reasonably efficient throughput so as not to slow down the manufacturing and assembly processing time.
In summary, the testing of semiconductor devices is an important part of the manufacturing process, and in order to prevent the processing time being seriously delayed, methods and apparatus need to be designed that facilitate the testing of such semiconductor devices in the most time-efficient and reliable manner possible.
When the dies are assembled into semiconductor packages, the packages are conventionally formed as part of what is called a leadframe. In the past a leadframe may include a single row of semiconductor packages, more recently however leadframes may include two or more rows of packages such that the semiconductor packages are arranged in an array. When they are attached to the leadframe, the packages are electrically isolated from each other and are physically connected to the leadframe by one or more tie bars. In this condition the devices are conventionally referred to as being non-singulated semiconductor devices. U.S. patent application Ser. No. 09/868,571 unknown filed Jun. 27 2001 entitled xe2x80x9cMethod and Apparatus for Testing Semiconductor Devicesxe2x80x9d and assigned to the assignee of the present application, the contents of which are incorporated herein by reference, describes an apparatus and method for testing non-singulated semiconductor devices.
Once the semiconductor devices have been separated from each other they are known as singulated devices. Various methods are known for testing singulated devices, but generally because the devices have been separated from the leadframe they must be tested individually one device at a time and this substantially increases the time required to test a number of such devices. This is particularly problematic when it is desired to carry out multiple tests per device, for example during environmental testing when the devices must be tested at different temperatures.
Conventionally, for example, tests on singulated devices must be carried out on substantially an individual basis. That is to say it is only possible to test one device (or at most 3 or 4) at a time. Conventionally for example, a test socket is used. A test socket receives one device at a time and is connected to a loadboard. At most perhaps four different test sockets can be located simultaneously on a single loadboard. The loadboard may be located within a thermal chamber to test a device (or as many as are provided on the loadboard) at a desired temperature.
Another method of testing individual devices involves slides. Devices to be tested are loaded into rails or tubes and are allowed to slide into a thermal chamber where they are brought to a desired temperature. One device at a time is loaded into a contactor mechanism that brings a test head into contact with the devices.
According to the present invention there is provided apparatus for supporting singulated electronic devices during a testing operation, comprising: a main body and a support member, wherein said support member is made of non-conducting high-resistivity material and comprises a plurality of recesses, each said recess being adapted to receive an individual singulated device.
Preferably means are provided associated with each recess for releasably holding a singulated device in the recess. For example the holding means may comprise suction means or gripping means.
In preferred embodiments of the invention the recesses are shaped so as to conform to the shape of a device to be received therein. In one example, each recess is formed with sides that taper inwardly towards the bottom of the recess, at least two raised projecting portions for supporting the leads of a device and for defining a space for receiving the body of a device. Such a recess would be useful for receiving devices formed with leads. Another example of a recess is shallow and formed with a flat bottom surface for receiving therein generally planar leadless devices.
Different support members may be used with the same main body depending on the nature of the devices to be tested, and the support members can be readily interchanged. Potentially a plurality of support members may be located on a single main body.
Preferably the main body is formed with an embedded heating element for heating electronic devices to be tested.
Viewed from another aspect the present invention also extends to apparatus for testing singulated electronic devices, comprising: a plurality of carrier means, each said carrying means being adapted to carry a plurality of singulated devices, input means for placing singulated devices onto said carrier means, at least one environmental control means for subjecting said devices to be tested to selected environmental conditions, a test head, means for removing tested devices from said carrier means for further processing, and means for conveying said carrier means between said input means, said environmental control means, said test head, and said removing means.
Viewed from a still further aspect the present invention extends to apparatus for testing singulated electronic devices, comprising: a plurality of carrier means, each said carrying means being adapted to carry a plurality of singulated devices, input means for placing singulated devices onto said carrier means, a test head, means for removing tested devices from said carrier means for further processing, and means for conveying said carrier means between said input means, said test head, and said removing means.
Viewed from a still further aspect the present invention extends to a method of testing singulated electronic devices, comprising: placing a plurality of singulated devices on a carrier means, conveying said carrier means to a test head, conveying said carrier means from said test head to an output location, and removing said singulated devices from said carrier means.